// Copyright 2015 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "net/base/backoff_entry_serializer.h"

#include <utility>

#include "base/strings/string_number_conversions.h"
#include "base/time/tick_clock.h"
#include "base/values.h"
#include "net/base/backoff_entry.h"

namespace {
// Increment this number when changing the serialization format, to avoid old
// serialized values loaded from disk etc being misinterpreted.
const int kSerializationFormatVersion = 1;
} // namespace

namespace net {

std::unique_ptr<base::Value> BackoffEntrySerializer::SerializeToValue(
    const BackoffEntry& entry,
    base::Time time_now)
{
    std::unique_ptr<base::ListValue> serialized(new base::ListValue());
    serialized->AppendInteger(kSerializationFormatVersion);

    serialized->AppendInteger(entry.failure_count());

    // Can't use entry.GetTimeUntilRelease as it doesn't allow negative deltas.
    base::TimeDelta backoff_duration = entry.GetReleaseTime() - entry.tick_clock()->NowTicks();
    // Redundantly stores both the remaining time delta and the absolute time.
    // The delta is used to work around some cases where wall clock time changes.
    serialized->AppendDouble(backoff_duration.InSecondsF());
    base::Time absolute_release_time = backoff_duration + time_now;
    serialized->AppendString(
        base::Int64ToString(absolute_release_time.ToInternalValue()));

    return std::move(serialized);
}

std::unique_ptr<BackoffEntry> BackoffEntrySerializer::DeserializeFromValue(
    const base::Value& serialized,
    const BackoffEntry::Policy* policy,
    base::TickClock* tick_clock,
    base::Time time_now)
{
    const base::ListValue* serialized_list = nullptr;
    if (!serialized.GetAsList(&serialized_list))
        return nullptr;
    if (serialized_list->GetSize() != 4)
        return nullptr;
    int version_number;
    if (!serialized_list->GetInteger(0, &version_number) || version_number != kSerializationFormatVersion) {
        return nullptr;
    }

    int failure_count;
    if (!serialized_list->GetInteger(1, &failure_count) || failure_count < 0)
        return nullptr;
    double original_backoff_duration_double;
    if (!serialized_list->GetDouble(2, &original_backoff_duration_double))
        return nullptr;
    std::string absolute_release_time_string;
    if (!serialized_list->GetString(3, &absolute_release_time_string))
        return nullptr;
    int64_t absolute_release_time_us;
    if (!base::StringToInt64(absolute_release_time_string,
            &absolute_release_time_us)
        || absolute_release_time_us < 0) {
        return nullptr;
    }

    std::unique_ptr<BackoffEntry> entry(new BackoffEntry(policy, tick_clock));

    for (int n = 0; n < failure_count; n++)
        entry->InformOfRequest(false);

    base::TimeDelta original_backoff_duration = base::TimeDelta::FromSecondsD(original_backoff_duration_double);
    base::Time absolute_release_time = base::Time::FromInternalValue(absolute_release_time_us);
    base::TimeDelta backoff_duration = absolute_release_time - time_now;
    // In cases where the system wall clock is rewound, use the redundant
    // original_backoff_duration to ensure the backoff duration isn't longer
    // than it was before serializing (note that it's not possible to protect
    // against the clock being wound forward).
    if (backoff_duration > original_backoff_duration)
        backoff_duration = original_backoff_duration;
    entry->SetCustomReleaseTime(
        entry->BackoffDurationToReleaseTime(backoff_duration));

    return entry;
}

} // namespace net
